Light projecting apparatus of scanner module and method for arranging light sources thereof

ABSTRACT

A light projecting apparatus of a scanner module and a method for arranging the light sources thereof is provided. The light projecting module includes a substrate, including a first end, a second end and a middle section, the first end and the second end respectively positioned at two sides of the middle section; and a plurality of light emitting diodes (LEDs), positioned on the substrate, an arrangement spacing interval being formed between the two adjacent light emitting diodes, the arrangement spacing interval being respectively decreased gradually toward the first end and the second end from the middle section.

CROSS-REFERENCES TO RELATED APPLICATIONS

This non-provisional application claims priority under 35 U.S.C. §119(a)on Patent Application No(s). 97122250 filed in Taiwan, R.O.C. on Jun.13, 2008, the entire contents of which are hereby incorporated byreference.

FIELD OF THE INVENTION

The present invention relates to a light projecting apparatus and amethod for arranging light sources thereof, and more particularly to alight projecting apparatus of a scanner module and a method forarranging light sources thereof.

BACKGROUND

Accompanying the progress of technology, optical scanners have alreadybecome a popular computer peripheral device. An image capturing methodfor an optical scanner mainly uses a light emitting device to projectlight onto a document. The light is guided to a light sensing elementthrough a lens set after being reflected by the document, and the lightsensing element can check and measure light with different strengthreflected from different areas on the document. The reflected light waveis then converted to digital data. Thereafter, scanning software is usedto read the data and reassemble it into a computer image file.

Please refer to FIGS. 1 and 2. An ideal light emitting device shouldhave a uniform brightness distribution, but the current scanner modulesmostly use a charge coupled device (CCD) as a light sensing element A1and a fluorescent tube A2 as a light emitting device so as to utilizethe fluorescent tube A2 to illuminate and scan a document A5 placed on aplatform A3, and reflect light emitted from the fluorescent tube A2 tothe document A5 through a light reflecting sheet A6. The result is thatthe light sensing element receives light unevenly, causing the lightreceived to be brighter at a middle part and dimmer at the parts of twosides, influencing the scanning quality after reflectors A4 reflectlight to CCD A1, because the brilliance of the fluorescent tube A2 atthe middle part thereof is much higher than the brilliance at the twoends thereof, or it is limited by a characteristic of an optical lens.

Due to the increase in environmental awareness, a fluorescent tube suchas external electrode fluorescent (EEFL) or cold cathode fluorescent(CCFL) used in the scanner module is gradually being replaced by otherlight sources, because it contains mercury or other harmful substances;a light emitting diode (LED) is currently one of the best substitutes.Accompanying the popularity of LEDs, a LED light strip structurereplacing the fluorescent tube has emerged; it is formed as a lightsource device similar to a fluorescent tube by connecting LED pellets toone another in series in an equidistant arrangement on a long-strip typesubstrate. However, the illumination brightness of the entire body hasthe same characteristic problem as the fluorescent tube, namely, thereis a significant drop between the brightness of a middle part thereofand the brightness of the two ends thereof. To solve this problem, thebrightness of the two ends can always be increased by means of firmware(F/W) compensation at the end of the process, to allow the brightness tobe as uniform as possible to achieve improved image brightness.

However, the manner mentioned above is unable to improve a signal/noiseratio (S/N ratio); the noise is also amplified after the brightness ofthe two ends is increased by means of the firmware (F/W), causing animage to be distorted.

SUMMARY OF THE INVENTION

For improving a light projecting structure of a scanner module to allowa light sensing element to receive light uniformly, the presentinvention is proposed.

For achieving the object mentioned above, the present invention proposesa light projecting apparatus of a scanner module, including:

-   a substrate, including a first end, a second end and a middle    section, respectively positioned at two sides of the middle section;    and-   a plurality of light emitting diodes (LEDs), positioned on the    substrate, an arrangement spacing interval being formed between the    two adjacent light emitting diodes, the arrangement spacing interval    being respectively decreased gradually toward the first end and the    second end from the middle section.

The present invention also proposes a method for arranging light sourcesof a scanner module, including the following steps:

-   providing a substrate;-   disposing a plurality of light emitting diodes on the substrate in    sequence according to a preset spacing interval;-   calculating the average brightness of each preset spacing interval;-   obtaining a plurality of arrangement spacing intervals corresponding    to the plurality of preset spacing intervals, forming a value of    each arrangement spacing interval which is directly proportional to    a percentage of average brightness of the corresponding preset    spacing interval to an entire brightness; and-   rearranging the plurality of light emitting diodes on the substrate    in accordance with the plurality of arrangement spacing intervals.

Accordingly, the first end, the second, and the middle section of thesubstrate may be positioned on the same horizontal plane or differenthorizontal planes.

Furthermore, a variation of the arrangement of the spacing interval fromthe middle section toward the first end may be different from avariation of the arrangement spacing interval from the middle sectiontoward the second, or the variation of the arrangement spacing intervalfrom the middle section toward the first end may be the same as thevariation of the arrangement spacing interval from the middle sectiontoward the second end.

In addition, the value of the arrangement spacing interval is inverselyproportional to the Nth power of the average brightness of thearrangement spacing interval (where N is larger than 0, and may be aninteger or a decimal); this is used for adjusting the brightness of themiddle section. For example, the value of the arrangement spacinginterval may be inversely proportional to the square or third power ofthe average brightness of the arrangement spacing interval. Furthermore,the brightness of the middle section is substantially 80% of thebrightness of either the first end or the second end.

The present invention arranges the plurality of light emitting diodes bymeans of continuous unequal spacing intervals, thereby enabling optimalbrightness uniformity. The image distortion caused from the firmware(F/M) process at the posterior end can be decreased substantially andthe image scanning quality can be further increased after the imagebrightness has been made more uniform by means of the process of animaging system (i.e. the S/N ratio at each one of the two ends isincreased).

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention can be more fully understood by reference to thefollowing description and accompanying drawings, in which:

FIG. 1 is a schematic view of a conventional scanner module structure;

FIG. 2 is a graph of a brightness curve of a conventional scanner;

FIG. 3 is a perspective view, showing a light projecting apparatusaccording to the present invention;

FIG. 4 is a plane view, showing a light projecting apparatus accordingto the present invention;

FIG. 5 is a schematic view, showing a structure applied in a scannermodule according to the present invention;

FIG. 6A is a graph, showing a brightness curve of a general lightprojecting apparatus according to the present invention

FIG. 6B is a graph, showing a LED light projecting apparatus accordingto the present invention; and

FIG. 7 is a flow chart, showing a method of arranging light sources on asubstrate according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Please refer to FIGS. 3, 4, 5, 6A and 6B. FIG. 3 is a perspective view,showing a light projecting apparatus according to the present invention.FIG. 4 is a plane view, showing a light projecting apparatus accordingto the present invention. FIG. 5 is a schematic view, showing astructure applied in a scanner module according to the presentinvention. FIG. 6A is a graph, showing a brightness curve of a generallight projecting apparatus according to the present invention. FIG. 6Bis a graph, showing an LED light projecting apparatus according to thepresent invention.

A light projecting apparatus 60 of a scanner module includes a substrate61 and a plurality of light emitting diodes (LEDs) 62.

The substrate 61 aproximates a long strip type, and includes a first end61 a, a second end 61 b and a middle section 61 c. The first end 61 aand the second end 61 b are respectively positioned at two sides of themiddle section 61 c, in which the first end 61 a, the second end 61 band the middle section 61 c are preferably positioned at the samehorizontal plane, but it is not limited to this according to the presentinvention; the first end 61 a, the second end 61 b and the middlesection 61 c of the substrate 61 may also be positioned at differenthorizontal planes.

The plurality of LEDs 62 are arranged on the substrate 61 in sequence,and an arrangement spacing interval 620 is formed between the twoadjacent LEDs 62. The arrangement spacing interval 620 is decreasedgradually from the middle section 61 c toward the first end 61 a and thesecond end 61 b respectively. Here, a variation of the arrangementspacing interval 620 from the middle section 61 c toward the first end61 a may be the same as a variation of the arrangement spacing interval620 from the middle section 61 c toward the second end 61 b, but it isnot limited to this according to the present invention; the variation ofthe arrangement spacing interval 620 from the middle section 61 c towardthe first end 61 a may also be different from the variation of thearrangement spacing interval 620 from the middle section 61 c toward thesecond end 61 b. Furthermore, the LED 62 may preferably be a white LED,and the plurality of LEDs 62 may be LEDs with different brightness, butit is not limited to these according to the present invention.

The value of the arrangement spacing interval 620 mentioned above isinversely proportional to the Nth power of an average brightness of thearrangement spacing interval 620, where the value of the arrangementspacing interval 620 may be inversely proportional to the square of theaverage brightness of the arrangement spacing interval 620, or the valueof the arrangement spacing interval 620 may be inversely proportional tothe third power of the average brightness of the arrangement spacinginterval 620; here the square and third power are only taken asexamples, but it is not limited to these according to the presentinvention.

Furthermore, a power module 611 is installed on one side of thesubstrate 61; it is connected to an external power to provide theplurality of LEDs 62 with necessary power for emitting light.

The brightness of the single LED 62 is first measured when the LEDs 62are arranged on the substrate 61, and the real brightness can then becalculated and estimated when the plurality of LEDs 62 are arranged tomake a light strip structure by distancing a preset spacing interval(i.e. by means of equidistance); namely that single light emittingcurves of all the LEDs 62 (in different positions), are added togetherto obtain an entire light emitting strength curve of the light stripstructure, and average brightness of each preset spacing interval isthen obtained (i.e. average brightness capable of representing thispreset spacing interval is obtained). Because the brightness is lower ifthe spacing interval between the two LEDs 62 is larger, supposing thatthe value of each arrangement spacing interval 620 is directlyproportional to a percentage of the average brightness of acorresponding preset spacing interval to the entire brightness, thevalue of each spacing interval 620 can then be obtained; the value is:

mth arrangement spacing interval Lm=(am)/(a1+a2+a3+ . . . +a(n−1)+an)

-   -   in which n=the number of the plurality of LEDs        -   am=the average brightness of mth preset spacing interval        -   m=1, 2, . . . , (n−1)

The plurality of LEDs 62 can then be arranged depending on the unequalarrangement spacing intervals 620 after the value of each arrangementspacing interval 620 is calculated, so as to ensure that uniformity ofbrightness is optimized (the brilliance thereof is show in FIG. 6A).

Here, the average brightness may be the brightness at a middle positionof the preset spacing interval or the arrangement spacing interval 620,but it is not limited to this in accordance with the present invention.

When the light projecting apparatus 60 projects scanning light toward adocument 80 placed on a scanning platform 10 and the scanning light isreflected by reflectors 30, as FIGS. 4 and 5 show, the strengths of thescanning light projected by the first end 61 a, the second end 61 b andthe middle section 61 c are the same, ensuring the document 80 receiveslight uniformly because the plurality of LEDs 62 are arranged on thelight projecting apparatus with the unequal arrangement spacingintervals 620. Image distortion caused from the firmware (F/M) processat the posterior end can be substantially decreased, and the imagescanning quality can be increased further after the brightness of animage processed by an imaging system becomes more uniform.

In addition, the plurality of the LEDs 62 may further be arranged withunequal spacing intervals 620 to cause the brightness of the middlesection 61 c to substantially be 80% of the brightness of either thefirst end 61 a or the second end 61 b and allow the brightness curve tobe lowered by approximately 20% at the middle section 61 c (thebrilliance thereof is shown in FIG. 6B), so as to allow the brightnessof a scanned image to be genuinely uniform because the imagingcharacteristic of a lens of the light sensing element 70 will also causethe middle brightness of the scanned image to be higher than theperipheral brightness thereof (the brightness of an imaging center is20% higher than an imaging peripheral).

Please refer to FIG. 7. The present invention also discloses a methodfor arranging light sources of a scanner module, including the followsteps:

Step 701: providing a substrate 61.

In this step, the substrate 61 approximates a long strip type, andincludes a middle section 61 c, a first end 61 a and a second end 61 bat two sides thereof, where the first end 61 a, the second end 61 b andthe middle section 61 c of the substrate 61 may preferably be positionedon the same horizontal plane and may also be positioned on differenthorizontal planes.

Step 702: installing a plurality of light emitting diodes (LEDs) 62 onthe substrate 61 in sequence by distancing a preset spacing interval.

The brightness of the single LED 62 is first measured when the LEDs 62are arranged on the substrate 61, and the plurality of the LEDs 62 arearranged on the substrate 61 to form a light strip structure bydistancing the preset spacing interval.

Step 703: calculating average brightness of each preset spacinginterval.

Real brightness is first estimated when the plurality of LEDs 62 arearranged to string up the light strip structure by distancing the presetspacing interval, namely that the illumination curves of the all LEDs 62(on different positions) are added together to obtain an entireillumination strength curve of the light strip structure, and theaverage brightness of each preset spacing interval is then obtained,where the average brightness may be the brightness at a middle positionof the preset spacing interval or an arrangement spacing interval 620.But it is not limited to this in accordance with the present invention.

Step 704: obtaining the plurality of arrangement spacing intervals 620corresponding to the plurality of preset spacing intervals, the value ofeach arrangement spacing interval 620 being directly proportional to thepercentage of the average brightness of the corresponding preset spacinginterval to the entire brightness.

The value of each arrangement spacing interval 620 is directlyproportional to a percentage of the average brightness of acorresponding preset spacing interval to the entire brightness. Thevalue of each spacing interval 620 can then be obtained; the value is:

mth arrangement spacing interval Lm=(am)/(a1+a2+a3+ . . . +a(n−1)+an)

-   -   in which n=the number of the plurality of LEDs        -   am=the average brightness of mth preset spacing interval        -   m=1, 2, . . . , (n−1)

Step 705: rearranging the plurality of LEDs 62 on the substrate 61depending on the plurality of arrangement spacing intervals 620.

The plurality of LEDs 62 can then be arranged depending on the unequalarrangement spacing intervals 620 after the value of each arrangementspacing interval 620 is obtained so as to ensure uniformity ofbrightness is optimized (the brilliance thereof is show in FIG. 6A).Because the imaging characteristic of a lens of the light sensingelement 70 will also cause the middle brightness of the scanned image tobe higher than the peripheral brightness thereof (the brightness of animaging center is 20% higher than an imaging peripheral), it may beassumed that the value of each arrangement spacing interval 620 isdirectly proportional to the Nth power of the percentage of the averagebrightness of the corresponding preset spacing interval to the entirebrightness (N is larger than 1, and may be an integer or decimal) inStep 704, and a brightness curve can then be achieved in which thebrightness of the middle section is lower than the both ends. The middlebrightness of the curve is designed to be approximately 20% lower thanthe other end in order to solve the imaging characteristic problem of alens (the brightness of an imaging center is 20% higher than an imagingperipheral). Depending on this demand, it may further be assumed that amiddle section curve is a parabola (the two ends of the parabola arerespectively the highest brightness point of a left section and thehighest brightness point of a right section, and the lowest brightnessat the center of the parabola is set to be 80% of the highest brightnessat the either end). The value of each arrangement spacing interval 620at the middle section can then be obtained in sequence according to thefollowing manner, after an equation of the parabola is obtained (here,assume that the value of each arrangement spacing interval 620 isdirectly proportional to the square of the percentage of the averagebrightness of the corresponding preset spacing interval to an entirebrightness). The value is

mth (counting from the highest point of the left end) arrangementspacing interval Lm==D*[(1/am)̂2]/[(1/a1)̂2+(1/a2)̂2+(1/a3)̂2+ . . .+(1/a(n−1))̂2+(1/an)̂2].

in which

-   D=the length from the highest brightness point of the first end to    the highest brightness point of the second end;-   n=the number of LEDs in the range of D;-   m=(n−1)

The plurality of LEDs 62 can then be arranged according to the unequalarrangement spacing intervals 620, after the value of each arrangementspacing interval 620 is obtained, to ensure the brightness of the middlesection 61 c is substantially 80% of the brightness of either the firstend 61 a or the second end 61 b, and ensure a part of the brightnesscurve at the middle section 61 c is approximately 20% less thebrilliance thereof is shown in FIG. 6B), so as to enable the brightnessof a scanned image to be genuinely uniform.

In addition, the D mentioned above is the length from the highestbrightness point at the first end to the highest brightness point at thesecond end, but it is not limited to this according to the presentinvention; it may also be a length from any chosen point in a section ofthe first end 61 a with gradually decreasing brightness to any chosenpoint in a section of the second end 61 b with gradually increasingbrightness.

A light projecting apparatus of a scanner module according to thepresent invention arranges a plurality of LEDs by means of continuousunequal spacing intervals; the LEDS are disposed on a first end and asecond end of a substrate by means of higher concentration and on amiddle section by means of looser disposition so as to ensure optimaluniformity of brightness. The image distortion caused from a firmware(F/W) process at a posterior end can be decreased substantially afterthe image brightness becomes more uniform through an imaging system(namely, a signal/noise (S/N) ratio of the either end is raised), andthe image scanning quality can be increased further.

Additional advantages and modifications will readily occur to thoseskilled in the art. Therefore, the invention in its broader aspects isnot limited to the specific details and representative embodiments shownand described herein. Accordingly, various modifications may be madewithout departing from the spirit or scope of the general inventiveconcept as defined by the appended claims and their equivalents.

1. A light projecting apparatus of a scanner module, comprising: asubstrate, comprising a first end, a second end and a middle section,the first end and the second end being respectively positioned at twoside of the middle section; and a plurality of light emitting diodes,positioned on the substrate, an arrangement spacing interval beingformed between the two adjacent light emitting diodes, the arrangementspacing interval being respectively decreased gradually from the middlesection toward the first end and the second end.
 2. The light projectingapparatus of a scanner module according to claim 1, wherein the firstend, the second end and the middle section of the substrate arepositioned on the same horizontal plane.
 3. The light projectingapparatus of a scanner module according to claim 1, wherein the firstend, the second end and the middle section of the substrate arepositioned on different horizontal planes.
 4. The light projectingapparatus of a scanner module according to claim 1, wherein theplurality of light emitting diodes are white light emitting diodes. 5.The light projecting apparatus of a scanner module according to claim 1,wherein the plurality of light emitting diodes are lighting emittingdiodes of different brightness.
 6. The light projecting apparatus of ascanner module according to claim 1, wherein the variation of thearrangement spacing interval from the middle section toward the firstend is different from the variation thereof from the middle sectiontoward the second end.
 7. The light projecting apparatus of a scannermodule according to claim 1, wherein the variation of the arrangementspacing interval from the middle section toward the first end is thesame as the variation thereof from the middle section toward the secondend.
 8. The light projecting apparatus of a scanner module according toclaim 1, wherein a value of the arrangement spacing interval isinversely proportional to the Nth power of an average brightness of thearrangement spacing interval.
 9. The light projecting apparatus of ascanner module according to claim 8, wherein a value of the arrangementspacing interval is inversely proportional to the square of an averagebrightness of the arrangement spacing interval.
 10. The light projectingapparatus of a scanner module according to claim 8, wherein a value ofthe arrangement spacing interval is inversely proportional to the thirdpower of an average brightness of the arrangement spacing interval. 11.A method for arranging light sources of a scanner module, comprising thefollow steps: providing a substrate; installing a plurality of lightemitting diodes on the substrate in sequence by placing them accordingto a preset spacing interval; calculating an average brightness of eachpreset spacing interval; obtaining a plurality of arrangement spacingintervals corresponding to the plurality of preset spacing interval, avalue of each arrangement spacing interval being directly proportionalto a percentage of the average brightness of the corresponding presetspacing interval to an entire brightness; and rearranging the pluralityof light emitting diodes on the substrate in accordance with thearrangement spacing intervals.
 12. The method for arranging lightsources of a scanner module according to claim 11, wherein the substratecomprises a first end, a second end and a middle section, the first endand the second end are respectively positioned at two sides of themiddle section.
 13. The method for arranging light sources of a scannermodule according to claim 12, wherein the arrangement spacing intervalis gradually decreased from the middle section toward the first end andthe second end respectively.
 14. The method for arranging light sourcesof a scanner module according to claim 12, wherein the first end, thesecond end and the middle section of the substrate are positioned on thesame horizontal plane.
 15. The method for arranging light sources of ascanner module according to claim 12, wherein the first end, the secondend and the middle section of the substrate are positioned on differenthorizontal planes.
 16. The method for arranging light sources of ascanner module according to claim 11, wherein the plurality of lightemitting diodes are white light emitting diodes.
 17. The method forarranging light sources of a scanner module according to claim 11,wherein the plurality of light emitting diodes are lighting emittingdiodes with different brightness.
 18. The method for arranging lightsources of a scanner module according to claim 11, wherein a value ofthe arrangement spacing interval is inversely proportional to the Nthpower of an average brightness of the arrangement spacing interval. 19.The method for arranging light sources of a scanner module according toclaim 18, wherein a value of the arrangement spacing interval isinversely proportional to the square of an average brightness of thearrangement spacing interval.
 20. The method for arranging light sourcesof a scanner module according to claim 18, wherein a value of thearrangement spacing interval is inversely proportional to the thirdpower of an average brightness of the arrangement spacing interval.